Dental flask



July 5, 1955 H. VILLA 2,712,158

DENTAL FLASK Filed Jan. 6, 1954 2 Sheets-Sheet 1 FIG-l IN VEN TOR.

HONORATO VILLA zyg AT TO Y H. VILLA DENTAL FLASK July 5, 1955 2 Sheets-Sheet 2 Filed Jan. 6, 1954 INVENTOR.

HONORATO VILLA BY j ATTO United States Patent 0 DENTAL FLASK Honcrato Villa, Mexico City, Mexico Application January 6, 1954, Serial No. 402,457

8 Claims. (Cl. 18- 33) This invention relates to improvements in a dental flask for use in molding dentures of various kinds including either partial or complete dentures.

in accordance with conventional practice, dental flasks are used for purposes of forming a mold having a cavity therein within which to cast either a partial or complete denture. A model of a denture first is placed in the rein and molding plaster is introduced'around the denture model while the plaster is in fluid state. Upon hardening, a plurality of complementary solidified plaster blocks result which respectively are containedih the several flask sections which interfit and are separable. Top and bottom plates coengage said sections was completely to enclose the plaster blockswith intheflaskwhen the flask sections are assembled. Aninlet' opening is formed in the top plate for the introductionofplaster into the flask,

After the model thus has been invested in the plaster, the two sections of the flask are separated so as to expose the denture model. The expendable portions of the den tu're model then are removed by well known; conventional processes and the plaster contained within the flask sections then has a cavity therein which constitutes a mold to receive denture base material One of said sections will have the incisal or occlusal portions of teeth embedded within the plaster therein but" at least the ridge laps and retentive areas of the teeth are exposed within said molding cavity.

Following the formation of the mold within the plaster blocks respectively formed in the sections of the flask referred to above, denture base material is introduced into the mold cavity so as to be united with the ridge laps and retentive areas of teeth contained in the plaster molds, the denture base material being either progressively packed within the cavity or introduced by injection through a suitable sprue opening. The moldeddenture then completely is enclosed. by the plaster in the several sections of the flask and removal of said plaster blocks from the flask for extrication of the molded. denture there.- from without danger of damage to the denture. is. difficult to achieve.

Various expedients have been resorted to. in the past and are used at present to efiect such removal of the plaster blocks from the flask but most of these expedients are rather crude, clumsy, time consuming, and frequently result in injury to the molded denture invested in the plaster. The plaster usually is. of a very hard. nature and resists fracture to a high. degree.

Many attempts have been made in the pastv to provide flask sections, each of which have. at least partially separable portions to facilitate the, removal ofthe molded plaster and denture. from the flask sections. Some of these flask sections have included members which are pivotally connected and utilize locking means to hold the members in assembled relationship. However, such. pivoted portions or members of the. flask sections, usually have abutting surfaces which more or less become coated with ice 2 desired to reassemble these portions or members of the flasksections into operative relationship, such coatings of plaster first should be removed from the abutting sure faces in order to insure correct positioning of the portions or members of each of the flask sections.

Other attempts to render flask sections so that they could be freed from the molded plaster more easily have comprised the formation of split flask sections which are somewhat resilient and, when the sections were released from locking means, said sections will separate somewhat at the split therein and thus tend to make the removal of the molded plaster unit easier. However, such resilient split sections have a tendency to permit the accumula: tion of liquid plaster on the abutting surfaces defining the split, as well as to become misshapen during continued use and misuse, especially if the walls of the split sections are relatively thick and an appreciable separation at the split is desired.

The present invention provides a dental molding flask which possesses at least all of the virtues of previously designed flasks and, in addition, the sections of the flask are unitary and continuous circumferentially but so shaped that, when a filler piece is removed from each section,

the flask sections may be rapped against a firm surface and quickly causes complete separation of the molded plaster unit from the flask sections.

The invention also provides simple and easily operated filler pieces for the flask sections, the entire construction being rugged and durable and capable of long life and use without any of the flask members or sections becoming distorted-or misshapen.

Further, the invention provides appropriate means by which the top and bottom covers for the flask sections. as well as the filler pieces, may be removed from the flask sections by simple and readily available means such as a trimming knife, screw driver or any other handy pointed tool or instrument.

Still further, the invention provides a dental molding flask having the foregoing advantageous characteristics yet being capable of being charged with denture base material by either a conventional packing process or an in; jection process.

Details of the invention as well as other objects thereofare set forth in the following specification and illustrated in the accompanying drawings comprising apart thereof.

In the drawings:

Fig. l is an exploded perspective view of the various components of a dental molding flask embodying the prin; ciples of the present invention.

Fig. 2 is a perspective view of the assembled components of the dental molding flask illustrated in Fig. 1.

Fig. 3 is a sectional view of the assembled flask shown on a smaller scale than Fig. 2 and taken on the line 3 3 of saidfigure.

Fig. 4 is a top plan view of the assembled flask with the top cover removed and illustrating, in broken lines, the position of the molded plaster unit after it has been dislodged from engagement with the interior walls of the flask sections.

Fig. 5 is a perspective view of another embodiment of the top cover for the flask unit, said cover being adapted for the injection molding of denture base material' Referring to Figs. 1 and 2 particularly, an exemplary flask assembly is illustrated which emphasizes the prin} ciples of the present invention. This assembly comprises an upper flask section 10 and a lower flask secfluid plaster during the molding operations and, when'itis 1 tion 12 which have flat surfaces on the bottom and top respectively that abut to. form a flask body 14. As will be seen from Figs. 1 and 4 particularly, the sections 10 and; 12 have. opposed: tapered side walls 16 joined: to a curved, wall 18 and a flat. end-wall 20. This shape, or:

one embodying at least some sort of tapered wall configuration, comprises one of the main features of the invention.

Section of the flask assembly is provided with aligning or guide lugs 22 which extend both above and below the top and bottom surfaces of section 16 as clearly shown in Fig.- 1, these lugs preferably being disposed within vertically extending recesses in the outer surfaces of the tapered side walls 16 of the section. Such recesses may be formed in any suitable manner such as by spaced ears clearly shown in Figs. 1, 2 and 4 and screws 24 or rivets are used fixedly to connect the lugs to the flask section.

The lower ends of lugs 22 preferably are tapered and are received within vertical grooves 26 in section 12, whereby sections 10 and 12 may very accurately be aligned when placed in operative position as illustrated in Fig. 2.

The flask assembly also is provided with a top cover 28, the perimeter of which closely conforms to the shape of the outer wall of section 10 and suitable notches 30 are provided on opposite sides of said cover to receive the upper ends of lugs 22 and thereby accurately position the cover relatively to said section when mounted thereon. While the cover 28 is co-extensive with the flask section 10 in a transverse direction, the straight edge 32 is disposed short of the inner surface of the flat end wall of section 10 for purposes to be described. Cover 28 also is provided with a plurality of vent and filling openings 34 in accordance with conventional practice.

The present invention also includes the use of space forming means comprising filler or spacer strips or blocks which extend into the interior of the flask sections 10 and 12 when assembled in molding position. The upper spacer or filler block 36 is illustrated in the upper portion of Fig. l, and in sectional view is shown in Fig. 3. The length of block 36 is such that it extends across section 10 between opposed walls 16 adjacent end wall 20. The inner surface of flat end wall 20 of section 10 also slopes inward and downward as shown in Fig. 3 and the abutting surface of filler block 36 is complementary to the inner surface of said flat end wall 20 as shown in said figure. integrally connected to the upper end of spacer block 36 is a top strip 38 which extends laterally from one surface of the spacer block 36 as shown in Figs. 1 and 3 and the ends of said top strip project beyond the ends of block 36. Thus, after the cover 28 has been positioned on the top of flask section 10, a space adjacent end wall 20 of said section is provided which receives spacer block 36 on the interior of said flask section. of block 36 by engaging the upper rim of section 10 and thereby positions accurately the spacer block relative to flask section 10, one side of strip 38 slidably abutting the straight edge 32 of cover 28.

A bottom cover plate 40 is also included in the assembly, the perimeters thereof conforming preferablyto the shape of the exterior walls of lower section 12 of the The top strip 38 limits the downward movement flask assembly. Preferably formed integrally with bottom plate 40 is an upstanding spacer or filler block 42 of suflicient length to extend across section 12 between the opposed side walls 16 thereof adjacent end wall 20. The outer surface of spacer block 42 slopes upward and inward, as shown in Fig. 3, in order to conform to complementary sloping surface on the interior of fla end wall 20 of section 12. No additional aligning mean are required between bottom plate 40 and section 12 of the flask inasmuch as the ends of spacer block 42 will rather closely engage the corners of the interior of se tion 12 where the flat end wall 20 connects with ti; tapered side walls 16 of said section. Preferably, the ends of spacer block 40 taper slightly inward and upward to facilitate the positioning of section 12 on said bottom plate.

When a pattern is to be invested within the flask sections, usually the lower flask section is placed upon hottom plate 40 and a suflicient amount of fluid plaster is placed therein to receive the model comprising teeth and expendable wax. The plaster is shaped and hardened, and the upper surface comprises a parting surface. This is coated suitably with plaster resisting material. The upper flask section 10 then is mounted upon section 12 and is filled with additional fluid plaster to completely enclose the model. Top cover 28 is then positioned on section 10 and the flask is finally filled in accordance with conventional practice by introducing the last required amounts of plaster through the vent and filling openings 34. This may be facilitated by subjecting the filled flask to vibration,

After the plaster has set an adequate period of time, he flask sections 10 and 12 then are separated along the parting line of the plaster blocks to permit the elimination of the expendable portions of the pattern, such as the wax, in order to form a mold cavity which is to receive the denture base material. The ridge laps and retentive areas of the teeth are exposed within said cavity. The denture base material then is packed within said cavity in accordance with conventional practice and the denture, enclosed within the plaster mold in the flask assembly, is permitted to cure at the desired temperature for the required period of time.

In order to remove the molded plaster block, in which the finished denture is invested, from the flask, the cover 28 or the upper spacer block is first removed from the flask assembly. The removal of these components is facilitated by the provision of a plurality of appropriately positioned tool receiving notches 44. In view of the tapered nature of spacer block 36, the top strip 38 and spacer block 36 readily become dislodged and removed from the assembly without injuring either the molded plaster block or the denture invested therein. The bottom plate 40 and spacer block 42 thereon next are removed from the still connected flask sections 10 and 12, due primarily to the tapered nature of spacer block 42. Such removal of the latter and bottom plate 40 likewise is accomplished without injury to the molded plaster block or the denture invested therein.

After both spacer blocks and the top and bottom covers thus have been removed from the connected flask sections 10 and 12, the latter still contains the molded plaster block which adheres to the inner surfaces of the flask. Said sections preferably now are positioned vertically as shown in Fig. 4 so that the flat end walls 29 of the sections 10 and 12 may be rapped, sharply if required, against a suitable flat surface. Because of the configuration of the tapered side wall 16 and curved wall 18 of both of the flask sections, such rapping of the flask sections and plaster block causes a dislodging or separation of the plaster block 44 from said inner surfaces of the mold sections due to the action of inertia and the provision of a clearance space adjacent the flat end walls 20 of the mold sections which is provided as a result of removing the spacer blocks 36 and 42.

After the plaster block 44 thus has been loosened and is positioned somewhat as illustrated by broken lines in Fig. 4 relative to the flask sections, said plaster block easily may be removed from the flask sections either by separating said sections or simply by letting the plaster block drop from said sections when the latter are disposed more or less horizontally. The plaster then is chipped from the molded denture in accordance with conventional practice.

It will be noted that the walls of the flask sections 10 and 12 are sufficiently thickthat said sections are capable of withstanding extensive use and even abuse without distorting or changing the shapes of said sections. Likewise, the spacer blocks 36 and 42 are relatively thick and rugged as are the top and bottom plates 28 and 40. The walls of the flask sections 10 and 12 are continuous and integrally connected, whereby strength is imparted to said sections and no abutting surfaces are formed on said sections upon which liquid or fluid plaster may accumulate and harden other than the top and bottom surfaces of each section. These surfaces preferably are smoothly finished and accurately fitted so that there is a minimum of separation, if any, between these surfaces of the flask sections when assembled as well as between said sections and the abutting surfaces of the top cover 28 and bottom plate 40. Thus, many of the difliculties presented in previously and presently used flasks have been obviated by the present invention and yet the removal of the molded plaster block and denture invested therein greatly is facilitated in a manner which is a marked improvement over previously developed flask structures.

In Fig. 5, another embodiment of top cover 46 is illustrated perspectively. The outline of this cover is similar to top cover 28 of the embodiment shown in Figs. 1 through 3. The cover 46 has the necessary vertical openings 48 and a pair of aligning notches 50 which receive the aligning lugs 22 of mold section 10. The

straight edge 52 of cover 46 cooperates with top strip 38 of filler block 36 similarly to the straight edge 32 of cover 28.

It will be noted however that cover 46 is provided with a large depending boss 54 through which a threaded opening 56 extends for receiving the threaded end of the injection type filling mechanism by which denture base material is injected into the mold cavity. Otherwise, the function of cover plate 46 is similar to that of cover plate 28 shown in Figs. 1 and 3.

While this invention has been shown and described in its several embodiments, and has included certain details, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways said plaster cast has hardened to provide a space within said flask sections adjacent said connecting wall of each and extending entirely across said sections between said opposed side walls thereof and into which space said plaster cast may be moved relative to said side walls of said-sections to separate the cast quickly from said flask sections.

2. The dental flask of claim 1 further characterized by the opposed side walls of said flask sections being tapered toward each other in plan view and said connecting wall of each section being substantially flat, and said filler block means also being insertable adjacent said flat wall of each section.

3. The dental flask of claim 1 further characterized by said filler block means comprising elongated blocks respectively insertable within said flask sections and disposed in vertically abutting relation to each other when positioned operably within said sections.

4. The dental flask of claim 3 further characterized by one of said filler blocks being fixed to one of said cover plate.

5. The dental flask of claim 4 further characterized by the other filler block having a strip fixed thereto and engageable with the rim of the other flask section.

6. A dental flask unit comprising in combination interfitting flask sections, each section in plan viewhaving a generally curved Wall terminating in oppositely tapering portions connected substantially at the ends thereof by a substantially straight wall, all of said walls being fixedly connected, top and bottom cover plates for said sections, and filler block means substantially as long as the inner flat surface of said straight walls of said sections and insertable within said flask sections adjacent said straight walls of said sections prior to molding therein a denture invested in cast plaster, said filler block means being removable therefrom after said plaster cast has hardened to provide a space within and extending entirely across said flask sections adjacent said straight walls and into which said plaster cast may be moved to separate the same quickly from all the inner surfaces of said flask sections.

7. The dental flask unit of claim 6 further characterized by said filler block means comprising elongated blocks respectively insertable Within said flask sections in abutting relationship to each other, said blocks being substantially as long as the straight walls of said flask sections and the ends of said blocks being substantially engageable with the tapering walls of said sections to position said blocks lengthwise relative to said sections.

8. The dental flask unit of claim 7 further characterized by one of said filler blocks being fixed to one of said cover plates and operable to position said plate relative to one of said flask sections and prevent appreciable movement therebetween in a plane parallel to said cover plate when assembled relative to said section.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,633 House June 19, 1945 2,440,910 Opotow May 4, 1948 2,471,205 Fagan May 24, 1949 FOREIGN PATENTS 97,808 Germany vOct. 20, 1898 

